Method for inhibiting the deposition of wax from wax-containing soluble oils and micellar dispersions and soluble oil and micellar compositions inhibited thereby

ABSTRACT

A method for inhibiting the deposition of wax from waxcontaining soluble oils and micellar dispersions in which a small amount of a was deposition inhibitor comprised of a copolymer of ethylene and a monoethylenically unsaturated ester is added to the soluble oil or micellar dispersion. Also disclosed are soluble oil and micellar compositions containing small amounts of the ethylene-ester copolymer.

P United States Patent Fischer et a1.

[ METHOD FOR KNBITING 2f:

DEPOSITKON OF WAX FROM WAX- CONTAINING SOLUBLE OlLS AND MICELLAR DKSPERSIONS AND SOLLE OIL AND CELL COOSITIONS INBIITED THEREBY Inventors: Paul W. Fischer, 11751 E. Beverly Blvd., Whittier, Calif. 90601; LeRoy W. Helm, 601 Elinor Drive, Fullerton, Calif. 92632 Filed: Jan. 8, 1971 Appl. No.: 105,089

US. Cl ..166/305 R, 166/304, 166/274, 252/855 B Int. Cl. .....C23f 11/12, C23f 15/00, E21b 43/25 Field of Search ..166/304, 305 R, 273275; 252/855 B, 8.55 D, 8.3, 56 R, 49.5; 134/40; 137/15; 260/285 AU, 87.3

References Cited UNITED STATES PATENTS 8/1962 Skolaut et a1. ..166/304 X 1 Aug. 8, 1972 Primary Examiner-Stephen J. Novosad Attorney-Milton W. Lee, Richard C. Hartman, Lannas S. Henderson, Dean Sandford and Robert E. Strauss [57] S 9: CT

A method for inhibiting the deposition of wax from wax-containing soluble oils and micellar dispersions in which a small amount of a was deposition inhibitor comprised of a copolymer of ethylene and a monoethylenically unsaturated ester is added to the soluble oil or micellar dispersion. Also disclosed are soluble oil and micellar compositions containing small amounts of the ethylene-ester copolymer.

35 Claims, No Drawings i ITION F G SOLUBLE OHS AND MICELL DISPERSIONS W SOLUBLE OIL AND NHCELLAR Bl" SONS :1 l ii ::z= 1 z :fIE BY This invention relates to the control of wax deposition from wax-containing soluble oils and micellar dispersions, and more particularly to a method for improving the filterability injectivity of these compositions into a porous media and to soluble oil and micellar compositions exhibiting improved filterability and injectivity.

Various soluble oils and micellar dispersions have been found useful in promoting the recovery of oil from oil-bearing subterranean reservoirs, in treating a permeable earth formation immediately surrounding a water injection well to increase the rate of injection of water into the formation, and in other well treating and oil recovery applications. These soluble oils and micellar dispersions are primarily admixtures of liquid hydrocarbon, one or more surface active agents, a stabilizing agent such as an oxygen-containing organic liquid, and they may also contain up to a major proportion of water. In the case of soluble oils and micellar dispersions employed in oil recovery, and often in the case of soluble oils and micellar dispersions employed in well treating, economics usually dictate that the liquid hydrocarbon employed in compounding the soluble oil or micellar dispersion be a crude oil that is available at the well site, and most desirably that lease crude previously recovered from the reservoir be employed.

Unfortunately, many crude oils otherwise available for compounding soluble oils and micellar dispersions contain wax and wax-like substances that are dissolved in the crude petroleum under reservoir conditions of pressure, temperature and gas saturation, but which on being cooled to ambient temperatures precipitate to form finely divided solid particles that are dispersed in the crude petroleum. Also, waxes and wax-like substances are present in other hydrocarbon fractions that would otherwise form a suitable base stock for the formulation of soluble oils and micellar dispersions. These solid waxy residues are present in the soluble oils and micellar dispersions formulated from the wax-containing crude petroleum, or other wax-containing hydrocarbon fraction, and upon their subsequent injection into the reservoir plug the exposed formation faces thereby causing the injection rate to be severely restricted or completely stopped. Also, it is conventional to filter the materials injected into a formation so as to minimize the presence of materials that would tend to plug the formation. It is often difficult or impossible to filter wax-containing soluble oils and micellar dispersions because the filters rapidly become plugged with wax.

Attempts have been made to avoid the wax deposition problem by heating the soluble oil and micellar dispersions sufiiciently to redissolve the wax. However, the soluble oils and micellar dispersions are often not stable at temperatures elevated sufficiently to redissolve the wax, and often cannot be maintained at a sufficiently elevated temperature during the injection process to avoid wax plugging. Also, attempts to control the wax deposition by the addition of inhibitors to prevent precipitation or agglomeration of the wax particles have been largely unsuccessful.

Accordingly, a primary object of this invention is to provide a method for inhibiting the deposition of wax from wax-containing soluble oils and micellar dispersions.

Another object of the invention is to provide a method for improving the injectivity of wax-containing soluble oils and micellar dispersions into permeable subterranean formations.

Still another object of the invention is to provide a method for increasing the filterability of wax-containing soluble oils and micellar dispersions.

A further object of the invention is to provide a method for inhibiting the tendency of wax-containing soluble oils and micellar dispersions to plug a permeable media through which they are flowed.

An even further object of the invention is to provide a method for lowering the minimum temperature at which a wax-containing soluble oil can be filtered and injected into a permeable subterranean formation without incurring substantial plugging.

A yet further object of the invention is to provide wax-containing soluble oil and micellar compositions that are filterable, that can be injected into a permeable subterranean formation without substantial plugging of the formation, and which are free of large particles of agglomerated wax.

Other objects and advantages of the invention will be apparent from the following description.

Briefly, this invention contemplates inhibiting the deposition of wax from wax-containing soluble oils and micellar dispersions by incorporating therein a small amount of an oil-soluble or oil-dispersible copolymer of ethylene and a monoethylenically unsaturated ester. The wax deposition inhibitor may be admixed into the wax-containing oil directly, or as a solution of the inhibitor dissolved in an organic solvent. Low concentrations of the agent inhibit the deposition of wax and wax-like substances from wax-containing soluble oils and micellar dispersions, increase the filterability of these materials, and reduce or inhibit the plugging of the formation with wax on the injection of the soluble oils and micellar dispersions into a permeable subterranean formation.

When solubleoils or micellar dispersions containing dissolved wax are cooled below the solidification temperature of the wax, solid wax precipitates are formed. These precipitates are mostly straight-chain paraffin hydrocarbons having emperical structures ranging from G l-I to C H- While the solid precipitates can be either crystalline or amorphorous, it is generally believed that in most cases parafiins precipitate from the soluble oil and micellar dispersions as spiney crystals having arms radiating out from a central nucleus. These crystals agglomerate or bunch together because of their spiney structures, and oil can be occluded within this structure. Some of the wax crystals or particles are too large to pass through the small openings in a porous filter media or permeable earth formation. These particles deposit on the face of the porous media causing plugging. Also, it is known that wax tends to deposit on irregular surfaces such as those found in a porous filter media or earth formation. Once wax starts to deposit on such surface, usually agglomeration continues until the porous media is completely plugged.

While the exact mechanism by which the wax deposition inhibitors of this invention inhibit the deposition of wax on porous media is not completely understood, it is injected that they function by inhibiting the formation of larger size wax crystals and by reducing agglomeration of the wax crystals so that they are more readily kept in suspension and exhibit less tendency to adhere to the exposed surfaces of the porous media. Also, these inhibitors may affect the deposition or attachment of the wax crystals to the surfaces which they contact. Thus, it is believed that these inhibitors affect both the size of individual wax crystals, and the tendency of the crystals to agglomerate and to adhere to solid surfaces. However, although the exact mechanism by which the inhibitors of this invention inhibit wax deposition from wax-containing soluble oils and micellar dispersions may not be completely understood, it has nevertheless been conclusively demonstrated that low concentrations of these agents are effective in inhibiting the deposition of wax in filters and in porous earth formations through which the wax-containing soluble oil or micellar dispersion is passed at temperatures below the solidification temperature of the wax. The term wax deposition is used herein to mean the precipitation and accumulation of wax and wax-like materials on the surfaces contacted by a wax-containing soluble oil or micellar dispersion, and not merely the precipitation of wax crystals or particles that remain dispersed in the soluble oil or micellar disper- 81011.

Also, it has been observed that the wax deposition inhibitors of this invention not only inhibit the deposition of wax and wax-like materials on surfaces which they contact, but also will in at least some cases disperse previously accumulated deposits of wax. Accordingly, the wax deposition inhibitors of this invention have utility both in inhibiting the deposition and accumulation of wax on surfaces contacted by a wax-containing soluble oil or micellar dispersion and in removing previously deposited wax from such surfaces.

The wax deposition inhibitors useful in the practice of this invention are substantially linear addition copolymers of ethylene and a monoethylenically unsaturated ester such as the vinyl and allyl esters of saturated aliphatic carboxylic acids and the saturated aliphatic esters of monoethylenically unsaturated aliphatic carboxylic acids. The monoethylenically unsaturated esters that can be copolymerized with ethylene to produce the desired copolymers are characterized by the formula:

wherein (l) R is hydrogen or an alkyl group containing from about one to 25 carbon atoms and R is a vinyl or allyl group, and preferably a vinyl group; or (2) R is an a,B-unsaturated alkylene and R is an alkyl group containing from about one to 25 carbon atoms.

Exemplary monoethylenically unsaturated esters that are copolymerizable with ethylene to form the copolymers useful as wax deposition inhibitors are the vinyl and allyl esters of formic, acetic, propionic, butyric, lauryic, palmitic and stearic acids; and the saturated aliphatic esters of acrylic acid and a-alkyl substituted acrylic acids such as methacrylic acid and the like. Also, ethylene can be copolymerized with a mixture of two or more of these esters to yield an ethylene/mixed ester copolymer.

Among the agents useful for inhibiting the deposition of wax from petroleum are copolymer ethylene/vinyl formate, copolymer ethylene/allyl formate, copolymer ethylene/ vinyl acetate, copolymer ethylene/allyl acetate, copolymer ethylene/vinyl propionate, copolymer ethylene/allyl propionate, copolymer ethylene/vinyl butyrate, copolymer ethylene/allyl butyrate, copolymer ethylene/vinyl laurate, copolymer ethylene/allyl laurate, copolymer ethylene/vinyl palmate, copolymer ethylene/allyl palmate, copolymer ethylene/vinyl stearate, copolymer ethylene/allyl stearate, copolymer ethylene/methyl acrylate, copolymer ethylene/ethyl acrylate, copolymer ethylene/butyl acrylate, copolymer ethylene/isobutyl acrylate, copolymer ethylene/Z-ethylhexyl acrylate, copolymer ethylene/methyl methacrylate, copolymer ethylene/ethyl methacrylate, copolymer ethelene/butyl methacrylate, copolymer ethylene/isobutyl methacrylate, copolymer ethylene/isodecyl methacrylate, copolymer ethylene/lauryl methacrylate, copolymer ethylene/tridecyl methacrylate, and copolymer ethylene/stearyl methacrylate.

The ethylene copolymerized with the ester tends to increase the oil solubility of the resulting copolymer. Thus, it is preferred that the copolymer contain a sufficiently high ethylene content to render it oil soluble or oil dispersible at the concentration employed. However, it has been found that increased ethylene content tends to reduce the effectiveness of the copolymer as a wax deposition inhibitors. Accordingly, it is within the scope of this invention to employ as a wax deposition inhibitor an ester polymer containing sufficient copolymerized ethylene to render the copolymer soluble or dispersible in oil.

Generally, it is preferred that the copolymer contain at least about 10 weight percent ester, and more preferably at least about 35 weight percent ester with the maximum ester content of the polymer not exceed ing that amount which renders the agent insoluble or difficult to disperse in oil under the conditions of use. Also, it is generally preferred that the copolymer exhibit a melt index between about 1 and 600 grams per 10 minutes. The term melt index as employed herein is the flow rate reported as the rate of extrusion in grams per 10 minutes as determined by ASTM test method Dl 238-65T entitled Measuring Flow Rates of Thermoplastics by Extrusion Plastometer and performed under Standard Test Condition E, ASTM Standards, American Society for Testing Materials, Part 27, June 1969, pages 455-466, which procedure is herein incorporated by reference.

Of the foregoing ethylene/ester copolymers useful in the practice of the invention, the lower vinyl esters and the lower alkyl acrylates and methacrylates are preferred in many applications.

Preferred copolymer combinations having a special utility as wax deposition inhibitors include copolymers of ethylene and vinyl acetate, ethyl acrylate and methyl methacrylate, i.e., copolymer ethylene/vinyl acetate, copolymer ethylene/ethyl acrylate and copolymer ethylene] methyl methacrylate.

One preferred class of agents particularly useful for inhibiting the deposition of wax from petroleum are ethylene/vinyl acetate copolymers containing from about to 70 weight percent vinyl acetate, and more preferably containing about 35 to 55 weight percent vinyl acetate, and exhibiting a melt index between about i and 600 grams per 10 minutes.

A particularly preferred agent having a special utility as a wax deposition inhibitor for petroleum is an ethylene/vinyl acetate copolymer containing about 39 to 42 weight percent vinyl acetate and exhibiting a melt index between about 45 to 70 grams per 10 minutes. An ethylene/vinyl acetate copolymer of this type especially useful as a wax deposition inhibitor is marketed by the E. I. duPont de Nemours Company under the trademark ELVAX 40.

The ethylene/ester copolymers useful as wax inhibitors are prepared by generally known techniques such as by copolymerizing ethylene and the ester monomer by free radical reaction at elevated temperatures and pressures. Any of a wide variety of free radical initiators such as small quantities of molecular oxygen or other known sources of free radicals including various peroxide compounds such as benzoyl peroxide, t-butyl hydroperoxide and the like can be employed to initiate the free radical reaction. Also, the catalyst can be ac tivated by the addition of a reducing agent such as sodium bisulfite or ferrous salts.

in practicing the method of this invention, an effective amount of the aforementioned wax deposition inhibitor is incorporated into a wax-containing soluble oil or micellar dispersion by any convenient mixing technique. It is to be recognized that the amount of wax deposition inhibitor required depends upon the properties of the particular soluble oil or micellar dispersion the amount and type of wax present in the oil, the temperature to which the soluble oil or micellar dispersion is cooled, the particular type and pore size of the porous media through which the soluble oil or micellar dispersion is passed, the roughness of the surfaces contacted by the oil, the specific inhibitor employed, and the degree to which it is desired to inhibit wax deposition. Thus, the optimum amount of wax deposition inhibitor required in any particular application will depend upon these factors, the cost of the inhibitor, and the cost of cleaning and downtime due to wax plugging. Treatment at concentrations in excess of optimum is not only costly, but in some cases is less efiective than the optimum concentration. The optimum treatment is best determined by actual field tests or by laboratory tests simulating field conditions.

Hence, broadly stated, this invention contemplates incorporating into a wax-containing soluble oil or micellar dispersion an amount of the above-described ethylene/ester copolymer effective to inhibit the deposition of wax from the soluble oil or micellar dispersion. While the exact amount of agent preferred in any particular application depends on the foregoing factors, nevertheless it has been found that the effec tive concentration of additive is between about 5 and 10,000 ppm based on the weight of soluble oil in micellar dispersion and in many applications the effective concentration is between about 5 and 200 ppm, and preferably less than about 60 ppm. Thus, it is within the scope of this invention to incorporate in a wax-containing soluble oil or micellar dispersion an effective amount of the inhibitor between about 5 and 10,000 ppm, and preferably between about 5 and 200 ppm.

The soluble oils used herein are oleaginous compositions which are miscible with oil and have the ability to spontaneously emulsify with water when admixed therewith to form micellar dispersions. These soluble oils comprise a liquid hydrocarbon, one or more selected surface active agents, and optionally, a stabilizing agent. The emulsions formed by the addition of water to a soluble oil are of the water-in-oil type, in that, at water concentrations less than the inversion concentration, oil is the continuous phase and the water is dispersed in the oil in the form of very fine droplets, or micelles, which are less than about 0.1 micron in size, and usually range in size from about to 600 A. These emulsions are generally transparent in appearance, and are stable in that they remain as microemulsions on aging. By transparent, it is meant that the microemulsions do not have a cloudy or opaque appearance, even though they contain color bodies. It is recognized, of course, that some cloudiness may appear at certain water concentrations without adversely effecting the utility of the microemulsion. Emulsions of this type are designated microemulsions to distinguish them from ordinary water-in-oil macroemulsions in which the lower limit in the size of the water droplets is about 0.1 micron. At water concentrations above the inversion concentration, the emulsion inverts to an emulsion of the oil-in-water type in which droplets of oil are dispersed in a continous water phase.

In many applications it is preferred to use soluble oils that are substantially anhydrous in that they contain little, if any, added water. However, it is well known that some of the ingredients from which soluble oils are compounded, such as the hydrocarbon, the stabilizing agent, and the petroleum sulfonate, can contain minor proportions of water and that is difiicult and costly to dehydrate these agents to remove all traces of water. Also, it may be advantageous when compounding the soluble oil to add a small amount of water to the composition. Thus, it is within the scope of this invention to inhibit wax deposition from anhydrous and substantially anhydrous soluble oils containing minor proportions of water, and from micellar dispersions containing major proportions of water. The term substantially anhydrous as used herein is meant to include soluble oils having not more than minor amounts of water. More particularly, these soluble oils contain less than about 10 volume percent water. The term micellar dispersions" as used herein is meant to include both oil-external and water-external, thermodynamically stable micellar solutions, microemulsions and transparent emulsions composed of hydrocarbon, surfactant, stabilizing agent and aqueous medium.

One of the major constituents of the soluble oil compositions useful in the practice of this invention is a liquid hydrocarbon, which can comprise a crude petroleum oil, such as a crude oil previously recovered from the reservoir, or other conveniently available crude oil; a refined or semi-refined petroleum product, such as gasoline, naphtha, stove oil and diesel; a residual product obtained by the distillation of lower boiling fractions from a crude oil, such as bunker fuel oil and other residual products; a low value refinery byproduct, such as catalytic cycle oil, lube oil extract, and the like; and liquefied normally gaseous hydrocarbons, such as propane, butane and LPG. While soluble oils can be prepared from any of these hydrocarbons, or mixtures of different hydrocarbons, in many applications it is preferred to use a soluble oil compounded with petroleum crude oil, such as crude oil previously recovered from the reservoir, or with other conveniently available crude oil. As mentioned previously, the crude oil or other hydrocarbon fraction from which the soluble oil or micellar dispersion is prepared often contains wax which precipitates as solid particles when the media is cooled below a critical temperature. This, invention is directed to the inhibition of wax deposition from soluble oils and micellar dispersions formulated with a wax-containing liquid hydrocarbon, and more particularly with a wax-containing crude oil.

Surface active materials which can be used are those that when admixed with the liquid hydrocarbon cause the formation of microemulsions of the water-in-oil type on the subsequent addition of water. Agents which exhibit this property can be defined by their hydrophilic-lipophilic balance and by their spreading coefficients. The hydrophilic-lipophilic balance is an indication of the size and strength of the hydrophilic, or water-loving, or polar groups, and the lipophilic, or oilloving, or non-polar, groups in a surfactant material expressed by a numerical value designated HLB number. The spreading coefficient is an indication of the facility with which one liquid spreads upon another liquid. Spreading coefiicients greater than indicate that the first liquid will spread on the second, and coefficients less than 0 indicate that the supernatant liquid will simply form floating lens-like drops. Accordingly, surface active materials, or mixtures of materials possessing the ability to spontaneously emulsify water in oil exhibit average HLB numbers of about three to seven, and the most negative spreading coefficient consistent with the system.

A number of surface active materials that exhibit the ability to spontaneously emulsify oil and water to produce water-in-oil microemulsions are commercially available. Among the preferred agents are various preferentially oil-soluble anionic surfactants such as the high alkyl aryl sulfonates, particularly the alkyl naphthenic monosulfonates. A particularly preferred surface active agent is an alkyl aryl monosulfonate prepared by sulfonation of an aromatic petroleum fraction. These sulfonates are preferably in the form of their sodium salts, however, other salts can be used.

It has been found that superior soluble oil and micellar compositions can be prepared by employing as the surface active agent a combination of preferentially oilsoluble organic sulfonates and preferentially water soluble organic sulfonates.

The preferentially oil-soluble surfactant material is an oil-soluble, relatively water-insoluble organic sulfonate that exhibits substantially greater solubility in oil than in water. Some of the preferentially oil-soluble organic sulfonates useful in the practice of this invention are almost completely insoluble in water, while others exhibit limited water solubility, particularly at elevated temperatures. Even though the preferentially oil-soluble organic sulfonates may exhibit some water solubility, they are nevertheless characterized by markedly greater solubility in oil. The preferentially water-soluble surfactant material is a water-soluble, relatively oilinsoluble organic sulfonate that exhibits substantially greater solubility in water than in oil. Some of these preferentially water-soluble organic sulfonates are almost completely insoluble in oil, while others exhibit limited oil solubility, particularly at elevated temperatures. Even though the preferentially water-soluble organic sulfonates may exhibit some oil solubility, they are nevertheless characterized by markedly greater solubility in water.

One class of preferentially oil-soluble organic sulfonates particularly useful in the practice of this invention are oil-soluble alkyl aryl sulfonates that contain only one sulfonic group attached to an alkyl aryl hydrocarbon. The preferentially oil-soluble alkyl aryl sulfonates are those which in the form of their sodium salts have molecular weights of more than about 400. Among the preferred preferentially oil-soluble organic sulfonates are alkyl sodium benzene monosulfonates and alkyl sodium polyaryl monosulfonates having molecular weights of more than about 400. The preferred preferentially water-soluble organic sulfonates include water-soluble alkyl aryl sulfonates. The water-soluble alkyl aryl sulfonates are generally those which in the form of their sodium salts have molecular weights of less than about 400 or which contain more than one sulfonic acid group per molecule. It has been found that in soluble oils compounded from petroleum crude oil or other high boiling hydrocarbons, superior results are obtained by employing as the preferentially oil-soluble organic sulfonate an alkyl aryl monosulfonate which in the form of its sodium salt has a molecular weight above about 450, and preferably in the range of about 450 to 550.

Thus, the soluble oil compositions of this invention are prepared by admixing into the hydrocarbon a preferentially oil-soluble organic sulfonate, such as an alkyl aryl monosulfonate or mixture of monosulfonates which in the form of their sodium salts have molecular weights of more than about 400, and a preferentially water-soluble organic sulfonate, such as an alkyl aryl sulfonate or mixture of sulfonates which in the form of their sodium salts have molecular weights of less than about 400 or which are polysulfonates. Alternatively, a mixture of preferentially water-soluble and preferentially oil-soluble sulfonates can be employed, such as a mixture of alkyl aryl sulfonates which in the form of the sodium salt have an average molecular weight in the range of about 400 to 500.

The preferentially oil-soluble alkyl aryl sulfonates and preferentially water-soluble alkyl aryl sulfonates useful in the practice of this invention can be prepared by sulfonating an appropriate alkyl aryl hydrocarbon or mixture of hydrocarbons. Thus, a preferred preferentially oil-soluble alkyl aryl sulfonate can be prepared by sulfonating an alkyl aryl hydrocarbon to yield an alkyl aryl sulfonate which in the form of its sodium salt has a molecular weight of more than about 400. The preferred preferentially water-soluble alkyl aryl sulfonates are prepared by selecting the alkyl aryl hydrocarbon so that when sulfonated, the resulting alkyl aryl sulfonate in the form of its sodium salt has a molecular weight of less than about 400, or by sulfonating sufficiently to form the polysulfonates. These sulfonates are preferably in the form of the sodium salt, however other salts can be used.

A readily available source of alkyl aryl sulfonates are the natural petroleum sulfonates produced by sulfonating a relatively narrow boiling range mixture of petroleum hydrocarbons. Depending upon the boiling range of the hydrocarbon fraction, on sulfonation, mixtures of alkyl aryl monosulfonates are produced which may be either preferentially water-soluble or preferentially oilsoluble. The term petroleum sulfonates" is a commercial designation of sulfonates which are obtained by a treatment of petroleum fractions, particularly solvent treated aromatic fractions, with sulfuric acid, fuming sulfuric acid, or sulfur trioxide, followed by neutralization to form the sulfonates. Upon sulfonation, two types of general products are formed which are designated mahogany acid and green acid. The terminology is based on the colors imparted to the respective oil and water phases produced in the sulfonation process, a brownish color being imparted to the oil phase by oil-soluble sulfonic acids and a greenish color being imparted to the aqueous phase by the water-soluble sulfonic acids. The mahogany acids and the green acids can be neutralized to fonn mahogany sulfonates and green sulfonates.

The mahogany sulfonates are alkyl aryl sulfonates which usually contain only one sulfonic group per molecule and both the green and the mahogany types contain mixtures of sulfonates of varying molecular weights with the mahogany, or oil-soluble sulfonates generally containing the sulfonates of higher molecular weights. The green sulfonates, or water-soluble sulfonates, contain the sulfonates of lower molecular weight or those containing more than one sulfonate group per molecule.

The preferentially oil-soluble surface active material and the preferentially watersoluble surface active material are employed in the proportions of about 1 part of preferentially oil-soluble agent per part of water-soluble agent to about 12 parts of oil-soluble agent per part of water soluble agent. Although the optimum surfactant combination is dependent upon the characteristics of the particular reservoir, in many operations it is found the superior results are obtained with a surfactant combination containing about one to four parts of preferentially oil-soluble surface active material per part of preferentially water-soluble surface active material; and more particularly, with a surfactant mixture containing about two parts of preferentially oil-soluble agent per part of preferentially water-soluble agent.

The various stabilizing agents that are admixed with the soluble oil to improve the properties and stability of the resulting microemulsions formed by admixing the soluble oil with water include partially oxygenated organic liquids such as monohydric and polyhydric alcohols, ketones, ethers and polyhydric alkyl ethers. Specific agents found particularly useful include isopropyl alcohol, secondary butyl alcohol, methyl ethyl ketone, glycol monoethyl ether, (Cellosolve), glycol monobutyl ether (butyl Cellosolve), and diethylene glycol monobutyl ether (butyl Carbitol). The terms Cellosolve and Carbitol are trademarks of the Union Carbide Company.

The preferred soluble oil or substantially anhydrous soluble oil compositions within the scope of this invention comprise about 52 to 90 volume percent of a waxcontaining liquid hydrocarbon, and more particularly a wax-containing crude oil; about 4 to 30 volume percent of a surface active material, such as alkyl aryl sulfonate obtained by sulfonation of an aromatic petroleum fraction; about 0.5 to 8 volume percent stabilizing agent; less than about 10 volume percent water; and about 5 to 10,000 ppm of the above described wax deposition inhibitor.

The preferred micellar dispersion compositions within the scope of this invention comprise about 4 to volume percent of a wax-containing liquid hydrocarbon such as a wax-containing crude oil; about 1 to 25 volume percent surface active material; about 0.01 to 6 volume percent stabilizing agent; about 10 to volume percent water; and about 5 to 10,000 ppm of the above described wax deposition inhibitor.

Where the liquid hydrocarbon has a relatively high viscosity, light liquid hydrocarbon can be added to reduce the viscosity of the resulting soluble oil or micellar dispersion. The light hydrocarbon will usually not constitute more than 25 volume percent of the resulting soluble oil. Also, the soluble oils and micellar dispersions of this invention can also contain electrolytes and other additives such as corrosion and scale inhibitors, bactericides, and the like.

The inhibited compositions of this invention can be prepared by any of the conventional techniques. One suitable method of preparing these compositions is to first admix the hydrocarbon base stock, surface active material and stabilizer in the desired proportions to form a substantially anhydrous soluble oil. Thereafter, if desired, water is added to obtain a substantially anhydrous soluble oil or micellar dispersion of the desired water content. Preferably, the water employed in forming the microemulsion is a salt-containing fresh water having a dissolved salt content of less than about 5,000 ppm. The wax deposition inhibitor can be incorporated into the soluble oil prior to the addition of water, or into the micellar dispersion formed on the addition of water thereto.

Although the wax deposition inhibitor can be added to the wax-containing oil directly, it is preferred that the additive be first dissolved or dispersed in an organic solvent such as naphtha, kerosene, diesel, gas oil, light crude oil, and other similar petroleum derivatives. Other suitable carriers include various alcohols, ketones, alkanes, cycloalkanes and aromatic solvents such as isopropyl alcohol, methyl ethyl ketone, hexane, cyclohexane, toluene, and the like. While the concentration of inhibitor in the solution can be varied over a wide range, the inhibitor solution generally contains between 2 and 50 weight percent of the-wax deposition inhibitor.

It is preferred that the wax-containing soluble oil or micellar dispersion be at a temperature above the solidification temperature of the wax when the wax deposition inhibitor is added, or that the soluble oil or micellar dispersion be heated to this temperature after the addition of the inhibitor. While this temperature varies somewhat depending upon the particular waxes present, it is within the scope of this invention to heat the wax-containing soluble oil to a temperature elevated sufficiently to dissolve the wax, either prior to or after addition of the wax-deposition inhibitor, but which is not sufficiently elevated to cause thermal degradation of the emulsion.

I A preferred method for incorporating the wax deposition inhibitor into a soluble oil or micellar dispersion is to first heat the soluble oil or micellar dispersion to a temperature not exceeding 150 F., and preferably not exceeding 120 F., sufficient to redissolve the wax, and while the soluble oil or micellar dispersion is maintained at this temperature, adding the wax inhibitor thereto in an amount sufiicient to obtain the desired inhibitor concentration. Thereafter, the soluble oil or microemulsion can be cooled to ambient temperatures without experiencing serious wax deposition.

The wax deposition inhibitors of this invention are compatible with soluble oils and micellar dispersions in that they do not cause degradation of the microemulsion, and at concentrations of up to at least 200 ppm exhibit no adverse effect upon the temperature stability range or apparent viscosity of the soluble oil or micellar dispersion, or upon its utility as an oil recovery or well treating agent.

The invention is further described by the following examples which are illustrative of specific modes of practicing the invention and are not intended as limiting the scope of the invention as defined by the appended claims.

EXAMPLE 1 These tests illustrate the improvement in filterability of a substantially anhydrous soluble oil obtained by the present invention. The soluble oil is prepared by admixing 74.9 volume percent of an unfiltered, wax-contaim ing Illinois crude oil having a gravity of about 39 API; 1 1.7 volume percent of a preferentially oil-soluble alkyl aryl sulfonate mixture containing about 62 weight percent of alkyl aryl sulfonates having a molecular weight between about 500 and 510 marketed by the Sonnebom Division of Witco Chemical Company under the trademark Petronate CR; 7.5 volume percent of a preferentially water-soluble alkyl aryl sulfonate mixture containing about 30 weight percent of alkyl aryl sulfonates having molecular weights between about 350 and 360 marketed by the Sonneborn Division of Witco Chemical Company under the trademark Pyronate 30; 1.9 volume percent diethylene glycol monobutyl ether marketed by Union Carbide Company under the trademark butyl Cellosolve; and 4.0 volume percent fresh water.

A first portion of the soluble oil is heated to a temperature of 1 F. and then cooled to a temperature of 70 to 75 F. and maintained at this temperature for a period of 24 hours. The soluble oil is then filtered through 0.45 micron filter paper. A filteration rate of 0.3 ml per minute is obtained.

A second portion of the soluble oil is heated to a temperature of 110 F. and, while the soluble oil is maintained at this temperature, there is added a quantity of a kerosene solution containing 2 weight percent of an ethylene/vinyl acetate copolymer marketed by the E. l. duPont de Nemours Company under the trademark ELVAX 40 sufficient to provide in the soluble oil a concentration of 40 ppm of the copolymer. This admixture is cooled to 70 to 75 F. and maintained at this temperature for 24 hours. The inhibited soluble oil is then filtered through 0.45 micron filter paper and a filtration rate of 8.1 ml per minute obtained.

The results of these tests are summarized in Table l.

TABLE 1 Wax Deposition Inhibitor Filtration Rate, content, ppm ml/min.

EXAMPLE 2 These tests illustrate the improvement in filterability of a micellar dispersion obtained by the present invention. A micellar dispersion is prepared by admixing 28.0 volume percent of an unfiltered, wax-containing lllinois crude oil having a gravity of about 39 API; 1 1.7 volume percent of a preferentially oil-soluble ammonium sulfonate mixture containing about weight percent of ammonium sulfonates having molecular weights between about 455 and 465; 3.0 volume percent primary normal amyl alcohol; and 57.3 volume percent water.

A first portion of the micellar dispersion is heated to 1 10 F. and then cooled to a temperature of 70 to F. and maintained at this temperature for a period of 24 hours. The micellar dispersion is then filtered through 0.45 micron filter paper. A filtration rate of 0.35 ml per minute is obtained.

Other portions of the micellar dispersion are separately heated to F. and, while the micellar dispersion is maintained at this temperature, there is added to each portion a quantity of a 2 percent solution of an ethylene/vinyl acetate copolymer marketed by the E. 1. duPont de Nemours Company under the trademark ELVAX 40 sufficient to provide micellar dispersions containing 20, 40 and 86 ppm of copolymer, respectively. The several portions of the micellar dispersions are cooled to 70 to 75 F. and maintained at this temperature for 24 hours. The various portions of the inhibited micellar dispersion are then filtered through 0.45 micron filter paper and the filtration rates measured.

The results of these tests are reported in Table 2.

TABLE 2 Wax Deposition Inhibitor Filtration Rate,

These tests demonstrate the conpatability of the wax deposition inhibitor of this invention and various other commercial wax deposition inhibitors with micellar dispersions.

A micellar dispersion is prepared in accordance with the method described in Example 2. Then 0.05 grams of various wax deposition inhibitors are added to a 25 m1 portion of the micellar dispersion and the appearance of the micellar dispersion is observed for a period of up to 24 hours. The various wax deposition inhibitors tested are:

l. A 2-percent solution of an ethylene/vinyl acetate copolymer marketed by E. l. duPont de Nemours Company under the trademark ELVAX 40 in kerosene.

2. Dow Paraffin Inhibitor E664 marketed by the Dow Chemical Company.

3. Enjay Parradine I-lO-20 marketed by the Enjay Chemical Company.

These tests illustrate the reduction in plugging experienced when flowing a substantially anhydrous waxcontaining soluble oil inhibited in accordance with this invention through a porous rock.

A substantially anhydrous soluble oil is prepared in the manner described in Example 1. A first portion of the soluble oil is heated to a temperature of 120 F., then cooled to a temperature of 75 F. and maintained at this temperature for a period of 4 hours. The soluble oil is then passed through a cylindrical Berea sandstone core 2-inches in diameter by a 3 7; inches long. The core exhibits an initial permeability of 155 millidarcies, but the permeability decreases to less than 10 millidarcies after about 1 pore volume of the soluble oil has been flowed through the core.

A second portion of the soluble oil is heated to a temperature of 120 F. and, while the soluble oil is maintained at this temperature, there is added a quantity of a kerosene solution containing 2 percent of an ethylene/vinyl acetate copolymer marketed by the E. l. duPont de Nemours Company under the trademark ELVAX 40 sufficient to provide in the soluble oil a concentration of 80 ppm of the copolymer. This admixture is cooled to a temperature of 75 F. and maintained at this temperature for 4 hours. The soluble oil is then passed through a cylindrical Berea sandstone core 2-inches in diameter by 3 55 inches long. The core exhibits an initial permeability of 153 millidarcies, and a permeability above 130 millidarcies after 3 pore volumes of the soluble oil have been flowed through the core.

EXAMPLE 5 These tests illustrate the reduction in minimum filtration temperature of a substantially anhydrous soluble oil obtainable by the practice of this invention.

A substantially anhydrous soluble oil is prepared according to the method described in Example 1. A first portion of the soluble oil is heated to a temperature of 1 F and then cooled to 85 F. and maintained at this temperature for a period of 24 hours. The soluble oil is then filtered through 0.45 micron filter paper. A filtration rate of 13 ml per minute is obtained.

A second portion of the soluble oil is similarly treated, excepting that it is cooled to a temperature of 75 F. A filtration rate of 0.3 ml per minute is obtained.

A third portion of the soluble oil is heated to a temperature of 110 F. and, while the soluble oil is maintained at this temperature, there is added a quantity of a kerosene solution containing 2 percent of an ethylene/vinyl acetate copolymer marketed by the E. l. duPont de Nemours Company under the trademark ELVAX 40 sufficient to provide in the soluble oil a concentration of 20 ppm of the copolymer. This admixture is cooled to F. and maintained at this temperature for 24 hours. The inhibited soluble oil is then filtered through 0.45 micron filter paper and a filtration rate of l 1.5 mil per minute obtained.

The later procedure is repeated excepting that the soluble oil is cooled to 68 F. A filtration rate of 7 ml EXAMPLE 6 This example illustrates the use of this invention to improve the rate of injection of a wax-containing micellar dispersion into an oil-bearing reservoir. It is desired to inject from about 1,600 to 3,000 barrels of the micellar dispersion into the reservoir through each of a plurality of wells so as to miscibly displace oil towards a number of spaced production wells.

Water is successfully injected into the reservoir prior to injection of the micellar dispersion, however, each well became plugged after the injection of only a few barrels of the micellar dispersion. ln the injection process, the micellar dispersion is heated to a temperature of 125 F. and filtered to remove solid impurities, but is cooled to a temperature of 55 F. at the reservoir face during injection. The reservoir temperature is approximately F.

Approximately 125 ppm of an ethylene/vinyl acetate copolymer marketed by the E. l. duPont de Nemours Company under the trademark ELVAX 40 is incorporated into the micellar dispersion at a temperature of F. This admixture is successfully injected into the reservoir at planned injection rates, even though the admixture is cooled to a temperature of 55 F. at the reservoir face.

"'Ethylene/vinyl acetate copolymer containing about 32 to 34 weight percent vinyl acetate and exhibiting a melt index of between about 22 to 28 grams per 10 minutes marketed by the E. l. duPont de Nemours Company under the trademark ELVAX 150.

EXAMPLE 8 The composition:

Vol. 1:

Wax-containing gas oil 31 Mixed alkyl aryl sulfonates l5 Secondary butyl alcohol 4 Water 50 Wax inhibitor 1,000

"Ethylene/vinyl acetate copolymer containing about 27 to 29 weight percent vinyl acetate and exhibiting a melt index of between about 22 to 28 grams per 10 minutes marketed by the E. l. duPont de Nemours Company under the trademark ELVAX 240.

Various embodiments and modifications of this invention have been described in the foregoing description and examples, and further modifications will be apparent to those skilled in the art. Such modifications are included within the scope of this invention as defined by the following claims.

Having now described the invention, we claim:

1. A method for inhibiting the deposition of wax from wax-containing soluble oils and micellar dispersions comprising incorporating into said soluble oil or micellar dispersion a wax deposition inhibitor comprised of a copolymer of ethylene and a monoethylenically unsaturated ester selected from the group consisting of (1) vinyl and allyl esters of saturated aliphatic carboxylic acids and (2) saturated aliphatic esters of unsaturated aliphatic carboxylic acids.

2. The method in accordance with claim 1 wherein said monoethylenically unsaturated ester is characterized by the formula:

wherein (l) R is hydrogen or an alkyl group containing from about one to 25 carbon atoms and R is a vinyl or allyl group, or (2) R is an a,B- unsaturated alkylene and R is an alkyl group containing from about one to 25 carbon atoms.

3. The method in accordance with claim 1 wherein said inhibitor is copolymer ethylene/vinyl acetate, copolymer ethylene/ethyl ethyl acrylate or copolymer ethylene/methyl methacrylate.

4. The method in accordance with: claim 1 wherein said inhibitor is incorporated into said wax-containing soluble oil or micellar dispersion as a solution of the copolymer dissolved in an organic solvent.

5. The method defined in claim 1 wherein the inhibitor is incorporated into said wax-containing soluble oil or micellar dispersion at a temperature sufficiently high to maintain the wax dissolved in the soluble oil or micellar dispersion, and wherein said soluble oil or micellar dispersion is thereafter cooled to a temperature below the solidification temperature of the wax.

6. The method defined in claim 1 wherein said inhibitor is incorporated into said wax-containing soluble oil or micellar dispersion in an amount to provide therein an effective concentration of said inhibitor between about 5 and 10,000 ppm.

7. A method for increasing the filtration rate of waxcontaining soluble oils and micellar dispersions which comprises incorporating into said soluble oil or micellar dispersion a wax deposition inhibitor comprising a copolymer of (l) ethylene and (2) a lower vinyl ester or a lower alkyl acrylate or methacrylate, said inhibitor being added to said soluble oil or micellar dispersion in an amount to provide therein a concentration of said copolymer between about 5 and 10,000 ppm effective to increase the rate of flow of said soluble oil or micellar dispersion through a porous filter media.

8. The method defined in claim 7 wherein said inhibitor is added to said soluble oil or micellar dispersion as a solution of the copolymer dissolved in an organic solvent.

9. The method defined in claim 7 wherein said inhibitor is a copolymer of ethylene and vinyl acetate containing from about 10 to weight percent vinyl acetate and exhibiting a melt index between about 1 and 600 grams per 10 minutes.

10. The method defined in claim 7 wherein the inhibitor is incorporated into said wax-containing soluble oil or micellar dispersion at a temperature sufficiently high to maintain the wax dissolved in the soluble oil or micellar dispersion, and wherein the soluble oil or micellar dispersion is thereafter cooled to a tempera- .ture below the solidification temperature of the wax.

11. A method for increasing the rate of injection of wax-containing soluble oils and micellar dispersions into permeable earth formations which comprises incorporating into said soluble oil or micellar dispersion a wax deposition inhibitor comprising a copolymer of l ethylene and (2) a lower vinyl ester or a lower alkyl acrylate or methacrylate, said inhibitor being added to said soluble oil or micellar dispersion in an amount to provide therein a concentration of said copolymer between about 5 and 10,000 ppm effective to increase the rate of injection of said soluble oil or micellar dispersion into a porous earth strata.

12. The method defined in claim 11 wherein said inhibitor is added to said soluble oil or micellar dispersion as a solution of the copolymer dissolved in an organic solvent.

13. The method defined in claim 11 wherein said inhibitor is a copolymer of ethylene and vinyl acetate containing from about 10 to 70 weight percent vinyl acetate and exhibiting a melt index between about 1 and 600 grams per 10 minutes.

14. The method defined in claim 11 wherein the inhibitor is incorporated into said wax-containing soluble 34. The composition defined in claim 33 wherein 35. The composition defined in claim 34 wherein said copolymer contains about 39 to 42 weight percent said copolymer exhibits a melt index between about 45 vinyl acetate and exhibits a melt index between about 1 to 70 grams per minutes.

and 600 grams perlO minutes. it s 

2. The method in accordance with claim 1 wherein said monoethylenically unsaturated ester is characterized by the formula: wherein (1) R is hydrogen or an alkyl group containing from about one to 25 carbon atoms and R1 is a vinyl or allyl group, or (2) R is an Alpha , Beta - unsaturated alkylene and R1 is an alkyl group containing from about one to 25 carbon atoms.
 3. The method in accordance with claim 1 wherein said inhibitor is copolymer ethylene/vinyl acetate, copolymer ethylene/ethyl ethyl acrylate or copolymer ethylene/methyl methacrylate.
 4. The method in accordance with claim 1 wherein said inhibitor is incorporated into said wax-containing soluble oil or micellar dispersion as a solution of the copolymer dissolved in an organic solvent.
 5. The method defined in claim 1 wherein the inhibitor is incorporated into said wax-containing soluble oil or micellar dispersion at a temperature sufficiently high to maintain the wax dissolved in the soluble oil or micellar dispersion, and wherein said soluble oil or micellar dispersion is thereafter cooled to a temperature below the solidification temperature of the wax.
 6. The method defined in claim 1 wherein said inhibitor is incorporated into said wax-containing soluble oil or micellar dispersion in an amount to provide therein an effective concentration of said inhibitor between about 5 and 10,000 ppm.
 7. A method for increasing the filtration rate of wax-containing soluble oils and mIcellar dispersions which comprises incorporating into said soluble oil or micellar dispersion a wax deposition inhibitor comprising a copolymer of (1) ethylene and (2) a lower vinyl ester or a lower alkyl acrylate or methacrylate, said inhibitor being added to said soluble oil or micellar dispersion in an amount to provide therein a concentration of said copolymer between about 5 and 10,000 ppm effective to increase the rate of flow of said soluble oil or micellar dispersion through a porous filter media.
 8. The method defined in claim 7 wherein said inhibitor is added to said soluble oil or micellar dispersion as a solution of the copolymer dissolved in an organic solvent.
 9. The method defined in claim 7 wherein said inhibitor is a copolymer of ethylene and vinyl acetate containing from about 10 to 70 weight percent vinyl acetate and exhibiting a melt index between about 1 and 600 grams per 10 minutes.
 10. The method defined in claim 7 wherein the inhibitor is incorporated into said wax-containing soluble oil or micellar dispersion at a temperature sufficiently high to maintain the wax dissolved in the soluble oil or micellar dispersion, and wherein the soluble oil or micellar dispersion is thereafter cooled to a temperature below the solidification temperature of the wax.
 11. A method for increasing the rate of injection of wax-containing soluble oils and micellar dispersions into permeable earth formations which comprises incorporating into said soluble oil or micellar dispersion a wax deposition inhibitor comprising a copolymer of (1) ethylene and (2) a lower vinyl ester or a lower alkyl acrylate or methacrylate, said inhibitor being added to said soluble oil or micellar dispersion in an amount to provide therein a concentration of said copolymer between about 5 and 10,000 ppm effective to increase the rate of injection of said soluble oil or micellar dispersion into a porous earth strata.
 12. The method defined in claim 11 wherein said inhibitor is added to said soluble oil or micellar dispersion as a solution of the copolymer dissolved in an organic solvent.
 13. The method defined in claim 11 wherein said inhibitor is a copolymer of ethylene and vinyl acetate containing from about 10 to 70 weight percent vinyl acetate and exhibiting a melt index between about 1 and 600 grams per 10 minutes.
 14. The method defined in claim 11 wherein the inhibitor is incorporated into said wax-containing soluble oil or micellar dispersion at a temperature sufficiently high to maintain the wax dissolved in the soluble oil or micellar dispersion, and wherein the soluble oil or micellar dispersion is thereafter cooled to a temperature below the solidification temperature of the wax.
 15. A method for inhibiting plugging of a porous media upon the passage of a wax-containing soluble oil or micellar dispersion through said media, which comprises incorporating into said soluble oil or micellar dispersion a wax deposition inhibitor comprising a copolymer of (1) ethylene and (2) a lower vinyl ester or a lower alkyl acrylate or methacrylate, said inhibitor being added to said soluble oil or micellar dispersion in an amount to provide therein a concentration of said copolymer between about 5 and 10,000 ppm effective to reduce plugging of the porous media by precipitated solid wax particles.
 16. The method defined in claim 15 wherein said inhibitor is added to said soluble oil or micellar dispersion as a solution of the copolymer dissolved in an organic solvent.
 17. The method defined in claim 15 wherein said inhibitor is a copolymer of ethylene and vinyl acetate containing from about 10 to 70 weight percent vinyl acetate and exhibiting a melt index between about 1 and 600 grams per 10 minutes.
 18. The method defined in claim 15 wherein the inhibitor is incorporated into said wax-containing soluble oil or micellAr dispersion at a temperature sufficiently high to maintain the wax dissolved in the soluble oil or micellar dispersion, and wherein said soluble oil or micellar dispersion is thereafter cooled to a temperature below the solidification temperature of the wax.
 19. A method for reducing the minimum temperature at which wax-containing soluble oils or micellar dispersions can be passed through a porous media without excessive plugging of the media by precipitated wax particles, which comprises incorporating into said soluble oil or micellar dispersion a wax deposition inhibitor comprising a copolymer of (1) ethylene and (2) a lower vinyl ester or a lower alkyl acrylate or methacrylate, said inhibitor being added to said soluble oil or micellar dispersion in an amount to provide therein a concentration of said copolymer between about 5 and 10,000 ppm effective to reduce the minimum temperature at which the wax-containing soluble oil or micellar dispersion can be passed through a porous media without excessive plugging of the media by participated wax particles.
 20. The method defined in claim 19 wherein said inhibitor is added to said soluble oil or micellar dispersion as a solution of the copolymer dissolved in an organic solvent.
 21. The method defined in claim 19 wherein said inhibitor is a copolymer of ethylene and vinyl acetate containing from about 10 to 70 weight percent vinyl acetate and exhibiting a melt index between about 1 and 600 grams per 10 minutes.
 22. The method defined in claim 19 wherein the inhibitor is incorporated into said wax-containing soluble oil or micellar dispersion at a temperature sufficiently high to maintain the wax dissolved in the soluble oil or micellar dispersion, and wherein the soluble oil or micellar dispersion is thereafter cooled to a temperature below the solidification temperature of the wax.
 23. The composition comprising about 4 to 90 volume percent of a wax-containing liquid hydrocarbon, about 1 to 30 volume percent surface active agents, about 0.01 to 8 volume percent of a partially oxygenated organic stabilizing agent, and about 5 to 2, 000 ppm of a copolymer of ethylene and a monoethylenically unsaturated ester characterized by the formula: where (1) R is hydrogen or an alkyl group containing from about 1 to 25 carbon atoms and R1 is a vinyl or allyl group, or (2) R is an Alpha , Beta -unsaturated alkylene and R1 is an alkyl group containing from about 1 to 25 carbon atoms.
 24. The composition defined in claim 23 wherein the composition is a micellar dispersion containing up to about 90 volume percent water present in the form of a microemulsion.
 25. The composition defined in claim 24 wherein said microemulsion is a water-in-oil microemulsion.
 26. The composition defined in claim 23 wherein said surface active agent is an admixture of preferentially oil-soluble organic sulfonate and preferentially water-soluble organic sulfonate.
 27. The composition defined in claim 23 wherein said partially oxygenated organic stabilizing agent is selected from the group consisting of isopropyl and secondary butyl alcohol, methyl ethyl ketone, glycol monoethyl ether, glycol monobutyl ether, and diethylene glycol monobutyl ether.
 28. The composition defined in claim 23 wherein said monoethylenically unsaturated ester is vinyl acetate.
 29. The composition defined in claim 28 wherein said copolymer contains 10 to 70 weight percent vinyl acetate.
 30. A composition comprising an admixture of about 4 to 90 volume percent of a wax- containing crude oil; about 1 to 30 weight percent of an admixture of preferentially oil-soluble organic sulfonate and preferentially water-soluble organic sulfonate; about 0.01 to 8 volume percent partially oxygenated organic stabilizing agent selected from The groups consisting of isopropyl and secondary butyl alcohol, methyl ethyl ketone, glycol monoethyl ether and diethylene glycol monobutyl ether; water; and about 5 to 10,000 ppm of a copolymer of (1) ethylene and (2) a lower vinyl ester or a lower alkyl acrylate or methacrylate.
 31. The composition defined in claim 30 wherein said admixture contains less than about 10 volume percent water present in the form of a water-in-oil microemulsion.
 32. The composition defined in claim 30 wherein said admixture is a micellar dispersion containing up to 90 volume percent water present in the form of a microemulsion.
 33. The composition defined in claim 30 wherein said copolymer is a copolymer of (1) ethylene and (2) about 10 to 70 weight percent vinyl acetate and wherein said copolymer exhibits a melt index between about 1 and 600 grams per 10 minutes.
 34. The composition defined in claim 33 wherein said copolymer contains about 39 to 42 weight percent vinyl acetate and exhibits a melt index between about 1 and 600 grams per 10 minutes.
 35. The composition defined in claim 34 wherein said copolymer exhibits a melt index between about 45 to 70 grams per 10 minutes. 